Objective Diffuse optical tomography (DOT) has low signal-to-noise ratio in the detection of big breasts in women, resulting in low imaging resolution. This paper proposed a way to improve the resolution of diffuse optical tomography, based on the computed tomography laser mammography (CTLM).Methods All experiments in this paper were phantom experiments. Firstly, this paper explored the effects of phantom diameter and target depth on the resolution of DOT. Secondly, this paper proposed to use the flexible photosensitive resin to make the outer covering part through 3D print, then use the outer covering part to constrain the measured object to reduce the diameter of the measured object to optimize the resolution of DOT, after verifying that the outer covering part had no significant effect on the resolution of DOT.Results In this paper, it was verified by phantom experiments that the changes of the phantom diameter and the target depth would affect the imaging resolution. With the increase of the phantom diameter, the wide-axis FWHM and the long-axis FWHM of the ROIs (region of interests) basically showed an upward trend. With the increase of the target depth, it was also affect the wide-axis full width at half maximum (FWHM) and the long-axis FWHM of the ROIs. The experimental results aslo found that the diameter of the phantom had a significant effect on the long-axis FWHM of the ROIs, and the target depth has a significant effect on the wide-axis FWHM of the ROIs. In addition, the results of the phantom experiment verified that the outer covering part had no significant effect on the resolution of DOT. Simultaneously, after compressing the measured object with the outer covering part, the long-axis FWHM of the ROIs decreased significantly, and the reduction reached more than 30%, which was much larger than the wide-axis FWHM of the ROIs. It was confirmed that it could achieve the effect of improving the imaging resolution by using the outer covering part to constrain the measured object.Conclusion The way proposed in this paper can achieve the effect of improving the resolution of breast diffuse optical tomography, and the materials and methods used were simple and had strong practicability, which provided a new idea for improving the resolution of breast diffuse optical tomography.